Pressure canner altitude chart: what pressure to use, and when to get your dial gauge tested

How to read the altitude chart

Find your elevation in the first column. Then read across to the kind of canner you own. That number is the pressure you hold for the whole processing time.

A weighted gauge has only two settings. It uses 10 pounds up to 1,000 feet and 15 pounds above that. A dial gauge reads any number, so it climbs one pound for each 2,000 feet.

These bands cover most low-acid foods, but not every one. The tested recipe for your food has its own altitude table, and that table always wins. On this page, we give the chart as a quick check, not a replacement.

One rule holds at every height. Never shorten the time or lower the pressure below the table. NCHFP says food may spoil if you "process for fewer minutes than specified." Skipping the altitude change above 1,000 feet can spoil it too.

Why altitude changes the number

As you go up, the air presses down less. So water boils at a lower temperature. The USDA Guide puts it this way: "Lower boiling temperatures are less effective for killing bacteria."

In a pressure canner, the heat comes from trapped steam. NCHFP says that "At sea level, a canner operated at a gauge pressure of 10.5 lbs provides an internal temperature of 240°F." Higher up, you need more pressure to reach the same heat. That is all the chart is doing.

The old rule was simpler and rougher. The 1942 USDA bulletin added 20 percent to water-bath times for each 1,000 feet. Today each tested recipe has its own altitude column, worked out for that food. NCHFP's guide to choosing the right processing time explains how to read them.

The dial gauge nobody has checked since 1990

Picture a canner on a basement shelf. It came from a parent or an estate sale. The dial still moves, the needle still points, and the lid still locks. It looks fine.

But a dial gauge can drift with age, and you can't see it drift. The problem is the one that reads high. You think the canner is at 11 pounds. It is really at 9. The food gets less heat than the recipe planned. NCHFP says: "Gauges that read high cause under-processing and may result in unsafe food."

The fix is cheap and once a year. Before canning season, call your county Cooperative Extension office. Many can test gauges. Bring the lid or gauge the way they ask, and write the result down.

If the gauge is off by 2 pounds or less, ask the tester how to adjust your target pressure. If it is off by more than 2 pounds, replace it. That is the same rule the 1942 bulletin gave. While you are at it, look at the gasket. NCHFP says "Nicked or dried gaskets will allow steam leaks."

A short checklist for canning day

• Look up your elevation in feet, once, and write it down.
• Find the altitude table in your tested recipe.
• Dial gauge? Make sure it was tested this year.
• Vent the canner for a full 10 minutes before you put on the weight or close the petcock.
• Start timing only when the canner reaches the target pressure.
• If the pressure drops below the target, bring it back and start the timing over.
• When time is up, let it cool on its own. The USDA Guide says "Do not force-cool the canner."

The NCHFP page on boiling-water and pressure canners has the full steps.

Where the book covers altitude and gauges

This is the problem The Lost Kitchen Skills, Checked was written for. Nancy Whitaker compares each old kitchen skill with current USDA, NCHFP and extension guidance, then badges it SAFE TODAY, UPDATE IT or RETIRED.

Pressure Canning for Beans, Meat and Soup has two cards for this page. Adjust for Altitude is badged UPDATE IT, since every recipe now has its own table. Get the Dial Gauge Tested is badged SAFE TODAY, because the 1942 rule still stands. A drawing shows the pressure by altitude for both kinds of gauge.

Water-Bath Canning for High-Acid Food shows how altitude changes water-bath times too, with the USDA peach table as an example.

The Pantry Workbook has a canning record with lines for your altitude, your gauge type and the date the dial gauge was last tested.

New to the pressure canner? Our page on why green beans can't go in a water bath explains what the canner is for.